Lab Activity 4: Blood Pressure (Using the Vernier ... - Cary Academy

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Lab Activity 4: Blood Pressure (Using the Vernier ... - Cary Academy

Lab Activity 4: Blood Pressure (Using the Vernier Probes)

Background Reading:

Blood pressure is a measure of the changing fluid pressure within the circulatory system. It varies

from a peak pressure produced by contraction of the left ventricle, to a low pressure, which is

maintained by closure of the aortic valve and elastic recoil of the arterial system. The peak

pressure is called systole, and the pressure that is maintained even while the left ventricle is

relaxing is called diastole (see Figure 1).

Mean arterial pressure (MAP) is not a simple average of the two pressures, because the duration

of diastole is twice that of systole. MAP is used by emergency room and intensive care unit

personnel as a measure of the adequacy of blood supplied to vital tissues (such as the brain,

heart, and kidneys) when the blood pressure is dangerously low.

Blood pressure is traditionally reported with the systolic pressure stated first and the diastolic

pressure stated second. In adults, 120/80 and below is considered normal blood pressure. High

blood pressure is 140/90 or above. The seriousness of low blood pressure, as well as the health

risks of high blood pressure (also called hypertension), have been elucidated over the past

several decades. High blood pressure is a major risk factor for a number of health problems

including strokes and congestive heart failure. Diet and exercise are beneficial, but many people

require medication for optimal blood pressure control.

In this experiment, you will examine your blood pressure using the Vernier Blood Pressure

Sensor. You will compare blood pressures taken before and after exposure to cold. The cold

stimulus activates the sympathetic nervous system, resulting in changes that prepare the body for

a “fight or flight” response (i.e., when fighting or running from danger).

The sensitivity of blood pressure to harmful external or internal injuries makes it useful as a vital

sign, an indicator of health, disease, excitement, and stress.

Figure 1. Systole versus diastole.

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Experimental Guide:

Materials:

computer

Vernier computer interface

Logger Pro

Vernier Blood Pressure Sensor

ice water bath

towel (paper or cloth)

Part I. Baseline Blood Pressure

1. Connect the Blood Pressure Sensor to the Vernier computer interface. There are two rubber

tubes connected to the pressure cuff. One tube has a black Luer-lock connector at the end

and the other tube has a bulb pump attached. Connect the Luer-lock connector to the stem

on the Blood Pressure Sensor with a gentle half turn.

2. Attach the Blood Pressure cuff firmly around the upper arm, approximately 2 cm above the

elbow. The two rubber hoses from the cuff should be positioned over the biceps muscle

(brachial artery) and not under the arm (see Figure 2).

3. Have the subject sit quietly in a chair with his or her forearm resting on a table surface. The

person having his or her blood pressure measured must remain still during data collection;

there should be no movement of the arm or hand during measurements.

4. Click to begin data collection. Immediately pump the bulb pump until the cuff

pressure reaches at least 160 mm Hg. Stop pumping. The cuff will slowly deflate and the

pressure will fall. During this time, the systolic, diastolic, mean arterial pressures, and pulse

will be calculated by the software. These values will be displayed on the computer screen.

When the cuff pressure drops below 50 mm Hg, the program will stop calculating blood

pressure. At this point, you can terminate data collection by clicking . Release the

pressure from the cuff, but do not remove it.

5. Enter the pulse and the systolic, diastolic, and mean arterial pressures in Table 1.

Part II. Blood Pressure Response to Cold

6. The subject will be instructed to place his or her opposite hand (the one to which the Blood

Pressure cuff is not attached) in the ice water bath for 15 s.

7. Collect data to examine the body’s response to cold.

a. With the cuff still attached, have the subject from Part I put the hand of his or her

non-cuffed arm in the ice water bath.

b. As soon as the subject’s hand enters the ice water bath, click .

c. Pump the bulb until the cuff pressure reaches at least 160 mm Hg, then stop pumping.

d. When data have been collected for 15 s, have the subject remove his or her hand from

the ice water bath.

e. The systolic, diastolic, and mean arterial pressures will be calculated by the software.

These values will be displayed on the computer screen. When the blood pressure

readings have stabilized (after the pressure drops to 50 mm Hg), the program will stop

calculating blood pressure. At this point, you can terminate data collection by clicking

. Release the pressure from the cuff, and remove the cuff from the subject’s arm.

10. Enter the systolic, diastolic, and mean arterial pressures, and the pulse in Table 2.

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Data:

Student 1-

Table 1–Baseline Blood Pressure

Systolic pressure

(mm Hg)

Diastolic pressure

(mm Hg)

Mean arterial pressure

(mm Hg)

Pulse

(beats/minute)

Table 2–Blood Pressure Response to Cold

Systolic pressure

(mm Hg)

Diastolic pressure

(mm Hg)

Mean arterial pressure

(mm Hg)

Pulse

(beats/minute)

Student 2-

Table 1–Baseline Blood Pressure

Systolic pressure

(mm Hg)

Diastolic pressure

(mm Hg)

Mean arterial pressure

(mm Hg)

Pulse

(beats/minute)

Table 2–Blood Pressure Response to Cold

Systolic pressure

(mm Hg)

Diastolic pressure

(mm Hg)

Mean arterial pressure

(mm Hg)

Pulse

(beats/minute)

Student 3-

Table 1–Baseline Blood Pressure

Systolic pressure

(mm Hg)

Diastolic pressure

(mm Hg)

Mean arterial pressure

(mm Hg)

Pulse

(beats/minute)

Table 2–Blood Pressure Response to Cold

Systolic pressure

(mm Hg)

Diastolic pressure

(mm Hg)

Mean arterial pressure

(mm Hg)

Pulse

(beats/minute)

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Data Analysis:

1. Describe the trends that occurred in the systolic pressure, diastolic pressure, mean arterial

pressure, and pulse with cold stimulus. How might these be useful in a “fight or flight”

response?

2. As a vital sign, blood pressure is an indicator of general health. A high blood pressure

(140/90 or higher) increases the risk of cardiovascular disease and strokes. Collect the

systolic and diastolic pressures for the class and calculate the average for each. Rate the

class average blood pressure using the following scale:

Blood Pressure

Category

140/90 or higher High

120–139/80–89 Pre-hypertension

119/79 or below Normal

Page 4 10/22/2006

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